False Dilemma refers to the fallacy of asserting the truth of the statement A or B when in fact both may be false. It is used in an argument of the form:
- Either A or B
- not A
- Therefore B
An argument of this form is most convincing when it is difficult to produce options other than A and B.
This is probably the most common fallacy and is known by several other names, including Black Or White (or Black And White), Bifurcation, False Dichotomy, Excluded Middle and Either/Or.
Example
The instance of this fallacy with the most far reaching consequences occurred during the Cold War. Both the United States Of America (USA) and the Union Of Soviet Socialist Republics (USSR) insisted that individuals, political groups and even entire countries must support one side or the other. The effects ranged from the 'communist witch-hunts' in the USA to proxy wars in Angola, Vietnam and Afghanistan.
A note on the continuum
False Dilemma is the most common logical fallacy, as in almost all cases there are more options than immediately apparent. For example, most questionnaires ask their participants if they are male or female. Even if the cases of transsexuals and transvestites are ignored, there are numerous genetic conditions (including possession of more than two sex chromosomes and non-expressiveness of Y-chromosome genes) that lead to someone not fitting the conventional definitions of either gender.
Further reading
For a comprehensive reference on logical fallacies and the principles of good argument, see Attacking Faulty Reasoning: A Practical Guide To Fallacy-Free Arguments:
- Attacking Faulty Reasoning... at Amazon.com
- Attacking Faulty Reasoning... at Amazon.co.uk (for British readers)